Lens with embedded occulting disc

This 1.6 cm diameter lens has a carefully-designed 3.5 mm diameter occulting disc embedded within it, to block straylight that spills around the edges of Proba-3's 1.4 m occulting disc mounted onto the Occulter spacecraft. This second occulting disc is located within the Proba-3 Coronagraph spacecraft. The two occulting discs together allow Proba-3 to view the corona to within 1.1 solar radii. The hole at the centre of the occulting disc is where the view of the corona is seen.